The metabolic response to injury in large part is a mechanism for the redistribution of labile protein from skeletal muscle to the viscera to meet the anabolic requirement for new protein such as the acute phase glycoproteins and leukocytic activity necessary for recovery from injury. In addition, fat stores are mobilized to meet the energy expenditure during periods of semistarvation. The purpose of this investigation is to identify the factors that initiate and control the response to injury. The hormonal/substrates response will be investigated in terms of its effect on protein and energy metabolism and changes in body composition. The key role of branched-chain amino acid oxidation in muscle in modulating this requirement by supplying energy substrates to muscle and gluconeogenic precursors, in the form of alanine and glutamine, to the liver will be investigated. The development of a supplement of branched-chain amino acids to already existing crystalline amino acid products will be studied, especially their ability to preserve protein synthesis and nitrogen balance, particularly in semi-starvation states where "ketoadaptation" is impaired. It is anticipated that this information will help us formulate guidelines for the development of new therapies for the injured patient.